The invention relates to a kit system for cemented prostheses, in particular for cemented knee prostheses, in which a prosthesis joint part is securable to a resected bone by means of bone cement.
With cemented prosthesis parts, the part is secured to a resected bone with bone cement, with the bone cement flowing into protrusions and recesses in the bones and the prosthesis and, on solidifying, anchoring both parts with respect to one another. In order to position the functional surfaces of prosthesis parts at the right place in spite of differing resections of the bone, different filler pieces have been developed in kit form which can enlarge the distance between the resected surface and the functional surface in steps.
For a metallic tibia platform which can be secured to a tibia by means of bone cement, it is possible to use intermediate plates of different thickness between the platform and the bearing shell. The securing of the bearing shell via an intermediate piece of this kind is however so problematic that many manufacturers prefer to use bearing shells of differing heights.
A further possibility involves in the use of intermediate plates of differing thicknesses which are secured to the underside of the tibia platform by screws and which can be cemented in along with the platform which has been secured to them. Thus the company Smith & Nephew Richards Inc., 1450 Brooks Rd., Memphis, Tenn. 38116, USA developed metallic intermediate plates of differing thickness and with structured surfaces which can be anchored both to the platform and to the bone with bone cement. Such anchorings have the disadvantage that, in addition to the anchoring between the bone cement and the tibia platform, two further anchorings with dovetail-like protrusions and recesses from the intermediate plate to the bone cement are required. Here it depends on the skill of the surgeon whether the bone cement actually flows into the undercuts at the intermediate plate.